Investigating the molecular epidemiology of Staphylococcal isolates from musculoskeletal infections associated with internal fracture fixation devices (StaphTyp) (V. Post) The aim of this study is to identify the key virulence factors retained by Staphylococcus aureus isolated from infections surrounding fracture fixation devices and survey the most prevalent virulence factors possessed by this organism. Over 350 bacterial isolates have been collected from Hospitals and University departments in Liestal, Luzern, Geneva and Freiburg in Switzerland and from two hospitals from Nantes and Lille in France. In collaboration with the Trauma center from Murnau Germany, the collection of prospective S. aureus as well as S. epidermidis isolates continues with increasing number of isolates (over 250 isolates as of End of 2013). Whole genome sequencing has been performed on the isolates. This study has highlighted significant trends regarding the virulence requirements displayed by S. aureus isolates associated with implant related infections in comparison to non-implant related infections. Ongoing whole genome sequencing will be required to examine genomic differences among the different infection cases. Pres: Biofilm formation & molecular characterization of Staphylococcus aureus isolated from orthopaedic implant related infections depends on type of device. Post V, Wahl P, Uckay I, Zimmerli W, Corvec S, Loiez C, Ochsner P, Moriarty TF. CORS Venice, Italy, 13th - 16th October 2013. Basic Science of Infection, T Fintan Moriarty, Asia Pacific Orthopaedic Association, Annual meeting Kuching Malaysia, August 2013. Partners: Wahl P (MD), Fribourg, Switzerland Zimmerli W (MD), Liestal, Switzerland Ochsner P (MD), Luzern, Switzerland Ilker U (MD), Geneva, Switzerland Corvec S (MD), CHU de Nantes, France Loiez C (MD), CHR Lille, France Militz M (MD), Murnau, Germany Development of new agents for the specific diagnostic imaging of infections associated with orthopedic devices (Imagin) (V. Stadelmann) Our infection imaging project aims to improve the understanding of the progression of bone infection and improve the diagnosis of infection by combining newly developed infection probes with functional imaging modalities. Current clinical gold standard methods target both septic (infectious) and aseptic conditions. Together with the CT Imaging focus area, we have followed the dynamic changes occurring in bone in a rat infected screw model using micro CT, which were verified postmortem by bacteriology, histology, and mechanical testing. This technique enables differentiation between infected and non-infected implants as early as three days, which is significantly shorter than conventional radiography. Furthermore, different species of bacteria have been shown to result in different patterns of bone loss: for example, S. aureus displays rapid osteolysis, which differs significantly from S. epidermidis, which results in slower and less significant bone loss. Therefore, this model follows clinical observations whereby S. aureus is an agent of acute infection, and S. epidermidis causes less acute, more chronic style infections. Figure 9.3.15: Bone reactions to a sterile screw (left) and an infected screw (right) analyzed via time-series of in-vivo microCT scans. (orange=quiescent, yellow=resorbed and red=new bone)
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